NEW Scottish Secretary Alistair Carmichael has warned against negative campaigning in the independence debate as he hit out at the "grossly offensive" language used by some nationalist supporters.

Mr Carmichael replaced Michael Moore in the role as part of the coalition's Cabinet re-shuffle on Monday, with Liberal Democrat leader Nick Clegg stating that the position now required "different experience".

The Lib Dem MP for Orkney and Shetland demonstrated why he is widely considered to be more combative than Mr Moore as he commented on the independence campaign so far.

He praised the work of Better Together leader Alistair Darling, who he said had done an "excellent job" in leading the pro-union campaign, but he warned against negative campaigning and complacency.

Independence supporters have accused Better Together of negativity, referring to the organisation as "Project Fear".

Speaking during a visit to the Scotland Office in Edinburgh, Mr Carmichael countered the claim.

He said: "It shouldn't be negative, because as a Scot and as somebody who feels proud to be British as well, I can be positive and proud of both aspects of my national identity.

"I think one of the things those of us who oppose independence do have to contend with is this assertion that every time we point out a problem we are being negative.

"It's not negative to point out that there are downsides to the SNP's oil fund.

"They know the negativity because they've been told that (privately) but they're not prepared to admit it."

Mr Carmichael said there was no place for offensive language in the debate.

Labour leader Johann Lamont referred to the "virus" of nationalism in her speech at the recent party conference, prompting nationalist supporters to tweet they were "yes positive".

"I think the use of the word virus wasn't necessarily a metaphor that I would have used," Mr Carmichael said.

"What I thought was crossing the line was the whole business of yes positive, that was distasteful."

He said social networking comments referring to Better Together supporters in Orkney as "quislings" were also "grossly offensive".

He said: "That is the sort of thing that if I see it coming from our side of the debate, yes, you might just see that on the odd occasion there is some justification for the label of bruiser, because anyone on our side of the debate who uses that kind of language will be bruised.